Many micro-invasive surgical instruments include a long, thin shaft, a tool on the distal end portion of the shaft and a handling device on the proximal end portion of the shaft. The tool includes, for example, a grasping, dissecting, biopsy or other forceps, a scissors or a needle holder with at least two straight or curved clamps, cutting edges or other jaw members of which at least one is movable. Alternatively, the tool includes another active device, for example a manipulator with a finger or a finger-shaped device or an electrode in hook form or other shape. The shaft contains (at least) one transmission rod, which as a rule is mounted in a closed channel in the interior of the shaft. The handling device includes one or more actuation devices that can move with respect to one another, for example two gripping parts, that medical staff can move in relation to one another with one hand. The proximal end portion and the distal end portion of the transmission rod are coupled with the actuation device or with the tool in such a way that a force exerted by medical staff onto the actuation devices or a relative movement of the actuation devices caused by medical staff can be transmitted to the tool, for example to move clamps toward one another or to press them together.
In using a micro-invasive surgical instrument of this type, the tool and a part of the shaft are inserted into a natural or artificial cavity in the patient's body, for example through a natural or artificial bodily opening. The development of micro-invasive surgical techniques tends toward using constantly smaller and, especially, fewer means of access. For example, in order to be able to work with an endoscope and two instruments in laparoscopic surgery by way of a single trocar, instruments with curved shafts can be used. An instrument with a curved shaft, however, cannot always be easily rotated around its longitudinal axis inside the access way in order to modify the orientation of the tool at its distal end portion.
In patent DE 10 2006 038 516 A1, a tubular medical instrument is described in which a tool 5, a shaft 3 and a handle 2 can be separated from one another for cleaning.
Patent DE 10 2008 015 418 A1 discloses a medical instrument with a curved shaft. A jaw member is detachably connected with a shaft by means of a bayonet lock. In connected position, the jaw member can be rotated with respect to the shaft. The shaft is detachably connected with a handle. The curved shaft can be rotated with respect to the handle by means of a hand wheel that is connected with an external shaft tube in torque-proof manner. An inside tube is connected to the handle with an additional hand wheel. The instrument can be configured as a unipolar or bipolar HF instrument.
Patent DE 10 2008 052 623 A1 discloses a surgical instrument with a jaw unit, a shaft and a gripping unit. The jaw unit is detachably affixed to the end of a shaft tube of the shaft and can rotate with respect to it.
To allow easy, thorough cleaning of the instrument, the tool, shaft and handling device of a micro-invasive surgical instrument, without use of auxiliary means, ought to be separable from one another and capable of being combined or coupled with one another. It is known, for example, from DE 10 2006 038 516 A1 how to configure the tool and the distal end portion of the shaft in such a way that the tool can be assembled and disassembled in a fully open assembled position. However, a few aspects both of the coupling of the tool with the shaft and of the coupling of the shaft with the handling device have not been sufficiently satisfactorily resolved to date, especially concerning the ability of the tool to turn or rotate with respect to the shaft when in coupled state.